The League of Nations might reserve in the mandate a right of supervision of administration and even of revocation of authority, but that right would be nominal and of little, if any, real value provided the mandatory was one of the Great Powers as it undoubtedly would be.

The almost irresistible conclusion is that the protagonists of the theory saw in it a means of clothing the League of Nations with an apparent usefulness which justified the League by making it the guardian of uncivilized and semi-civilized peoples and the international agent to watch over and prevent any deviation from the principle of equality in the commercial and industrial development of the mandated territories.
It may appear surprising that the Great Powers so readily gave their support to the new method of obtaining an apparently limited control over the conquered territories, and did not seek to obtain complete sovereignty over them.

It is not necessary to look far for a sufficient and very practical reason.

If the colonial possessions of Germany had, under the old practice, been divided among the victorious Powers and been ceded to them directly in full sovereignty, Germany might justly have asked that the value of such territorial cessions be applied on any war indemnities to which the Powers were entitled.

On the other hand, the League of Nations in the distribution of mandates would presumably do so in the interests of the inhabitants of the colonies and the mandates would be accepted by the Powers as a duty and not to obtain new possessions.